1. Field of the Invention
The invention relates to a vehicular data recording apparatus and method and, more particularly, to a data recording apparatus and method that records running data of a vehicle.
2. Description of the Related Art
A data recording apparatus of a vehicle, such as a motor vehicle or the like, is disclosed in, for example, Japanese Patent Application Laid-Open No. 7-249137. The data recording apparatus records running data (driving data) regarding the vehicle by storing the data into a storage device in a sequential overwrite manner. When the magnitude of acceleration of the vehicle is equal to or greater than a reference value, the apparatus determines that the vehicle has entered an abnormal state, and stops the overwrite storage of data into the storage device.
Since the data recording apparatus records running data of the vehicle into the storage device in the sequential overwrite manner, the storage device of the apparatus does not need to have a large storage capacity. Furthermore, since the data recording apparatus stops the overwrite data storage into the storage device when the magnitude of acceleration of the vehicle becomes equal to or greater than the reference value, the data recording apparatus is able to reliably store running data provided immediately before the magnitude of vehicle acceleration becomes equal to or greater than the reference value.
However, since the data recording apparatus is constructed so as to determine that the vehicle has entered an abnormal state when the magnitude of vehicle acceleration becomes equal to or greater than the reference value, the data recording apparatus sometimes fails to detect an abnormal state although the vehicle is actually in an abnormal state. More specifically, the acceleration of a vehicle becomes relatively great in some cases during normal running of the vehicle. Therefore, in a data recording apparatus that determines whether the vehicle is in an abnormal state on the basis of only the magnitude of acceleration of the vehicle, the reference value for the determination as to whether the vehicle is in an abnormal state needs to be set to a relatively large value. Hence, in some cases, although an abnormal state, such as a crash of the vehicle or the like, has actually occurred, the data recording apparatus fails to detect the abnormal state, and therefore fails to store running data provided immediately before the occurrence of the abnormal state of the vehicle.